Re: T5 issues
I beat the hell out of the 4cyl trans in my '86 Vert. The T5 behind my 347 in my '85 though, I lost second gear syncros. A bit of a power difference for sure, but sometimes they hold, sometimes they don't.
If you want to put serious power down, go with a TKO500 or 600 and you'll be banging gears with no problems. I went with the TKO600 in my '85 and it held everything I threw at it.
A quick comment about Lucas additives though, JUNK, IMO. All it is, is gear oil and soap. I wouldn't put it in my lawnmower.....